Will polls overestimate Republican support again?

Op-ed: Donald Trump has moved closer to Hillary Clinton in many polls, but she still holds a lead. Some leading pollsters had Mitt Romney ahead in 2012, only to see a Democratic landslide.

Will the same thing happen this year? There are signs that Clinton is ahead in most swing states, and that even the Senate could be taken over by Democrats.

538 warns that there is no guarantee her strong position in the swing states means she will win in the electoral college.
However, the election site also says: “Overall, Clinton’s leads in the tipping-point states — the ones most likely to determine the Electoral College winner in a close election — average about 4 percentage points, close to her numbers in national polls.”

It is difficult to determine how to fit reports that show Trump is losing badly among some increasingly important demographic groups, including Hispanics, African-American, millenials and women.

How important these groups will be depends to a large extent on how many turn out. Trump has not charmed them, but Clinton remains distrusted.

Reviewing how polls were done is no guarantee that a reader will be able to separate the wheat from the chaff. There are so many issues, though one can be tracked fairly easily.

Does a pollster consistently lean towards Republicans or Democrats? Even that may not mean they will likely be wrong.
We do know the white population has not been growing as fast as other groups as birth rates decline.

“The U.S. electorate this year will be the country’s most racially and ethnically diverse ever. Nearly one-in-three eligible voters on Election Day (31%) will be Hispanic, black, Asian or another racial or ethnic minority, up from 29% in 2012. Much of this change is due to strong growth among Hispanic eligible voters, in particular U.S.-born youth.

We do know the white population of registered voters has grown less than other groups.

“An analysis of changes in the nation’s eligible voting population – U.S. citizens ages 18 and older – offers a preview of profound U.S. demographic shifts that are projected to continuefor decades to come. While the nation’s 156 million non-Hispanic white eligible voters in 2016 far outnumber the 70 million eligible voters that are racial or ethnic minorities, their growth lags that of minority groups. As a result, the non-Hispanic white share of the electorate has fallen from 71% in 2012 to 69%,” the Pew Research Center reports.

“There are 10.7 million more eligible voters today than there were in 2012. More than two-thirds of net growth in the U.S. electorate during this time has come from racial and ethnic minorities. Hispanics, blacks, Asians and other minorities had a net increase of 7.5 million eligible voters, compared with a net increase of 3.2 million among non-Hispanic white eligible voters.”

Keep in mind, some minority groups are more likely to vote than others.

Although Clinton had trouble with millenials when she was battling Bernie Sanders, the younger voters have taken the advice of Sanders and seem likely to vote for her now.

“Democratic presidential nominee Hillary Clinton is consolidating the support of the Millennials who fueled Bernie Sanders' challenge during the primaries, a new USA TODAY/Rock the Vote Poll finds, as Republican Donald Trump heads toward the worst showing among younger voters in modern American history.

“The survey shows Clinton trouncing Trump 56%-20% among those under 35, though she has failed so far to generate the levels of enthusiasm Sanders did — and the high turn-out that can signal — among Millennials.”

CNN had a poll with Trump leading that was outdated several hours after it came out by a Washington Post poll that showed Clinton winning when all 50 states were polled.